Device for controlling selector switches in automatic telephone systems



y 1956' HANS-JOACHIM JABCZYNSKI 2,7

DEVICE FOR CONTROLLING SELECTOR SWITCHES IN AUTOMATIC TELEPHONE SYSTEMS Filed Dec. 1, 1952 Inventor:-

d m Jmciim 2% United States Patent 2,744,164 DEVICE FOR CONTRGLLING SELECTOR SWITCEHES IN AUTOMATIC TELEPHONE SYSTEMS Hans-Joachim Jabczynski, Berlin-Zehlendorf, Germany, assignor to Siemens 8: Halske rrlrtiengesellschaft, Munich, Germany, a corporation of Germany Application December 1, 1952, Serial No. 323,355 Claims priority, application Germany December 13, 1951 4 Claims. (Cl. 179-18) This invention is concerned with a device for controlling the operation of selector switches, especially hunting switches in signalling systems, e. g., in automatic tele phone systems, by circuit control means including an electron discharge tube.

The principal object of the invention is to assure reliable stopping of a hunting selector switch with its wipers in engagement with bank contacts associated with a selected line or trunk in a group of lines or trunks extending in a certain trafiic direction.

This principal object is realized by the provision of a discharge tube comprising a cathode and a plate and a pair of control electrodes, the cathode being connected with the test wiper of the hunting selector switch to conduct thereto the idle potential from the test conductor of an idle line when the test Wiper reaches such idle line, a device for controlling the operative actuation of said discharge tube, said device comprising an impulse source for producing periodically efiective series of nonoverlapping marker impulses respectively assigned to groups of lines extending in different tratfic directions, including a series of marker impulses assigned to the group of lines including the selected idle line which extends in a certain one of said trafiic directions, a control wiper individual to said hunting selector switch for conducting the corresponding series of marker impulses to one of said control electrodes of said discharge tube, an auxiliary switch cooperating with said hunting selector switch for conducting such series of marker-impulses to the other control electrode, said discharge tube being operatively effective responsive to the simultaneous occurrence of said marker impulses on said control electrodes in the presence of said idle potential of the selected idle line on the cathode thereof, and a relay connected to the plate of said discharge tube and energized thereby responsive to operative actuation thereof for stopping said hunting selector switch with its wipers in engagement with the bank contacts associated with the idle line to seize such line.

The term line is intended to embrace the meaning ordinarily attributed to the term trunk.

The discharge tube therefore evaluates three marker impulses or signals, namely, the signal which designates the desired traflic direction; the signal which becomes effective when the selector switch involved reaches the bank contacts of a line or trunk branching in the desired traflic direction; and the signal which corresponds to the potential on an idle line or trunk reached by the switch during the hunting operation thereof. The simultaneous evaluation of these three marker signals by the discharge tube results in speeding up the operations required in extending calls, as compared with systems in which these signals are evaluated separately or successively.

The simultaneous evaluation of the marker impulses or signals is particularly desired when the hunting switch operates in the nature of a by-pass selector switch which has access to by-pass trunks in case all the direct trunks normally accessible thereto should be found busy. The invention also ofiers the possibility of employing a single r 2,744,164 Patented May 1, 1956 ice control conductor extending, e. g., between a hunting selector switch ofthe by-pass type and a coacting rotary marker switch which is set in accordance with the desired traffic direction. All corresponding contacts of the individ ual rotary coacting switches and of the by-pass selector switches may be connected in multiple, so that only simple wiring changes are required in case of changes in the network plan or scheme of the corresponding system.

The invention is not restricted to use with. selector switches operating as switches for selecting by-pass trunks. It may be equally well used in connection with hunting selector switches which are employed for seizing idle trunks branching in desired traflic directions. ing selector switches may be, for example, rotary switches or switches of the vertical-rotary type. The invention is, however, not inherently limited to use with such switches.

An example of the invention will now be described with reference to the accompanying drawing showing in diagrammatic manner pertinent circuit details in connection with a hunting selector switch of the by-pass type.

The selector switch UW may be employed for extending calls over by-pass trunks at times when all direct trunks are busy. Three trunk groups I, II, III are for this purpose accessible to the switch UW. The desired trafl'ic direction is marked by a switch MW which is temporarily associated with the selector switch and which is set responsive to the receipt of dial pulses designating the desired trafiic direction. In case all direct trunks in the desired traflic direction are busy, the call will be switched to the by-pass selector switch UW, and this switch is now operated to seek an idle by-pass trunk in one of the trunk groups I, II or III which has been marked by the switch MW. The latter switch may be disposed in a switch frame remote from switch UW.

The switch MW may be set to place its wiper in engagement with one of several associated bank contacts, of which three bank contacts 1, 2 and 3 are shown. The various trafiic directions are marked by short periodically recurring marker or signal impulses, three of which are by way of example diagrammatically indicated at P1, P2 and P3. The impulses are at difierent instants sequentially, i. e., nonoverlapping transmitted by a suitable impulse generator. An impulse generator suitable for this purpose is disclosed in copending application Ser. No. 301,647, filed July 30, 1952. In accordance with the wiring indicated in the drawing, the marker or signal impulses P1, P2 and P3 will at successive instants be efiective at the bank contacts 1, 2 and 3, respectively, of the marker switch MW. An impulse occurring at any given instant also becomes efiective at a segmental bank contact I, II, III accessible to the wiper d of the selector switch UW. The segmental bank contacts I, II, III correspond respectively to the trunk groups I, II, III accessible to the wipers a, b, c of the switch UW. The signal impulses P1, P3 and P3 thus become simultaneously effective at the respective segmental bank contacts I, II and III and at the corresponding bank contacts 1, 2, 3 of the marker switch MW.

Assuming now that the wiper of the switch MW has been set in engagement with bank contact 2, the signal or marker impulse P2 will be connected to and will appear at the grid of the discharge tube R0 Which is connected with conductor G1. The identical signal impulse P2 will also appear on the grid of the tube R0 which is connected with conductor .62 at the instant when the wiper d of the switch UW engages theassociated segmental bank contact 11. The grids connected to conductors G1 and G2 accordingly receive a bias from the voltage source 66V which operates to block the operation of the tube incident to the sweeping of the test wiper c of the switch UW over associated bank contacts. A potential will appear at the grid connected with conductor G1 to cause The huntthe tube to fire only when the wiper c engages the bank contact of an idle trunk in the desired trunk group, which is designated by an idle potential of 60 volts connected thereto over a resistor (about 1900 ohms) and provided that a potential is simultaneously present which designates the desired tratfic direction, i. e., in the assumed case a voltage corresponding to the signal impulse P2. The generator which produces the signal or marker impulses is for this purpose on a voltage of 66 volts, i. e., at a potential which corresponds to that connected to the resistors Wll and Wi2. The signal impulse P2 appears in the assumed example on the grid of the tube R connected with conductor G1 over the wiper of the switch MW on bank contact 2 and simultaneously also on the grid connected with the conductor G2 over the wiper d of the switch UW in engagement with the segmental bank contact II. The simultaneous occurrence of the signal impulse P2 on these grids is periodically repeated so as to prepare the tube R0 to fire.

The tube becomes conductive only when the wiper c of the switch UW finds an idle trunk in the trunk group II. A suitable corresponding potential (60 volts over a resistance of about 1000 ohms) will at such instant appear on the cathode of the tube R0, which is picked up by the test wiper c on the test conductor of the idle trunk.

Relay P having the windings I (about 1000 ohms) and 11 (about 60 ohms) is now energized in a circuit from ground, tube R0, wiper c and the test conductor of the idle trunk. The relay P energizes and operates suitable contact means (not shown) to stop further operation of the switch UW. Details of the stepping circuit of the switch and of its various control circuits have not been shown, in order to avoid encumbering the drawing. Relay P also operates its contact 1p, thereby placing itself in a holding circuit independent of the tube R0, thus extinguishing the tube and providing a busy potential for the seized trunk. The line conductors of the seized trunk are switched through over the contacts 2p and 3p of the relay P and line wipers a and b of the switch UW.

It will be appreciated from the foregoing explanations that the switch UW is stopped by the operation of the tube R0 only in response to three marker signals simultaneously connected thereto, namely, at the instant when there is an identical marker or signal impulse on the grids connected to conductors G1 and G2 and when a potential is connected to the cathode of the tube which marks an idle trunk in the trunk group in which the switch UW has been hunting to extend a desired connection.

The invention has been described in connection with specific switches used in an automatic telephone system, to give an example thereof. It will be understood of course that the invention may be used with other types of switches and in different signalling systems, and that the appended claims are therefore intended to embrace variations that may fall within their scope and spirit.

I claim:

1. In an automatic telephone system having groups of lines branching respectively in different trafiic directions, each group comprising a plurality of lines, and having a hunting selector switch comprising wipers including a test wiper and drive means for stepping said wipers to seek a line in a desired group and to seize such line if idle, each idle line carrying a potential to mark its idle condition, a circuit arrangement for stopping the hunting operation of said selector switch with its wipers in engagement with an idle line to be seized, said circuit arrangement comprising an electron tube having a cathode connected with said test wiper to conduct to said tube the potential marking the line to. be seized as idle, a control relay connected in the plate circuit of said tube, a pair of control electrodes for said tube, and a device. for simultaneously connecting to .said control electrodes of said tube marker impulses which designate the trflfiic direction of the idle line to be seized, said device comprising an impulse source for producing said marker impulses, a wiper forming part of said hunting selector switch for connecting said impulse source to one of said control electrodes, and a control switch cooperating with said hunting switch and having a wiper for connecting said impulse source with the other one of said control electrodes, said tube becoming conductive responsive to the simultaneous connection of said marker impulses produced by said source to its control electrodes and connection to the cathode thereof of the potential marking said line to be seized as idle for the purpose of energizing said relay to stop said hunting selector switch with its wipers in engagement with the idle line.

2. The arrangement and cooperation of parts according to claim 1, wherein said control relay comprises a high resistance winding connected with the plate of said tube and a low resistance winding connected, in series with said high resistance winding, and contact means operated by said, control relay upon energization thereof for shunting said high resistance winding and said tube, to extinguish said tube, and for connecting said low resistance. winding-with the test wiper of said hunting sclector switch to connect over such low resistance winding a potential to the test conductor of the seized line marking said line as busy.

3. In a signalling system, a plurality of groups of lines, each group comprising several lines respectively extending in diiferent trafiic directions, each line in each group comprising line conductors and a test conductor, an impulse source. for producing periodically eifective series of marker impulses respectively assigned to the respective groups of lines, a hunting selector switch having wipers including a test wiper for hunting an idle line in a group of said lines, an idle marking potential connected to the test conductor of an idle line, and a circuit arrangement for controlling the operation of said hunting selector switch in seizing an idle line in the corresponding group of lines, said circuit arrangement comprising a discharge tube having a cathode and a plate and having a pair of control electrodes, circuit means for connecting said cathode with said test wiper to conduct thereto the idle marking potential on the test conductor of the corresponding idle line when said test wiper reaches such idle line, and, a device for simultaneously conducting to said pair of control electrodes of said discharge tube periodically eifective marker impulses from said impulse source which are assigned to the group of lines including said idle line, said device comprising a control wiper individual to said hunting selector switch for conducting said marker impulses to one of said control electrodes, an auxiliary switch cooperating with said hunting selector switch for conducting said marker impulses to the other control electrode, said discharge tube being operatively elfective responsive to the simultaneous occurrence of said marker impulses on said control electrodes in the presence of said idle marking potential on the cathode thereof, and relay means connected to the plate of said discharge tube and energized thereby upon operativeactuation thereof for stopping said hunting selector switch with its wipers in engagement with the conductors of said idle line to seize such line.

4. The arrangement and cooperation of elements as defined in claim 3, comprising contact means actuated by said relay means upon energization thereof for com pleting a circuit having the triple function, namely, first, of closing a holding circuit for itself, second, extinguishing said, discharge tube, and third, placing busy marking potential on the test conductor of the seized line.

References Cited in the tile ofthis patent UNITED STATES PATENTS 

